Bacterium capable of producing L-amino acid and method for producing L-amino acid

Abstract

A bacterium is described which belongs to the Enterobacteriaceae family, and has an ability to produce an L-amino acid, such as L-glutamic acid, L-arginine and L-threonine. The bacterium is modified so that the activity of a protein encoded by ydcI gene is decreased, thereby producing and accumulating the L-amino acid selected from L-glutamic acid, L-arginine, and L-threonine in the culture medium or cells of the bacterium when cultured in a culture medium. Subsequently, the L-amino acid is collected from the culture medium or the bacterium.

1. A bacterium belonging to the Enterobacteriaceae family that is able to produce an L-amino acid selected from the group consisting of L-glutamic acid, L-arginine, L-threonine, and combinations thereof, and said bacterium is modified so that the activity of a protein encoded by ydcI gene is attenuated as compared to an unmodified bacterium. 
     
     
       2. The bacterium according to  claim 1 , wherein the activity of the protein encoded by ydcI gene is attenuated by decreasing the expression of the ydcI gene or by disrupting the ydcI gene. 
     
     
       3. The bacterium according to  claim 1 , wherein the protein encoded by ydcI gene is selected from the group consisting of:
 A) a protein comprising the amino acid sequence shown in SEQ ID NO: 2, 12 or 14; and 
 B) a protein comprising the amino acid sequence shown in SEQ ID NO: 2, 12 or 14, except that one or several amino acids are substituted, deleted, inserted or added, and wherein said protein has DNA binding activity. 
 
     
     
       4. The bacterium according to  claim 1 , wherein said ydcI gene is selected from the group consisting of:
 (a) a DNA comprising the nucleotide sequence shown in 301-1221 of SEQ ID NO: 1, 301-1230 of SEQ ID NO: 11, or 301-1218 of SEQ ID NO: 13; and 
 (b) a DNA which hybridizes under stringent conditions with a DNA comprising the nucleotide sequence shown in 301-1221 of SEQ ID NO: 1, 301-1230 of SEQ ID NO: 11, or 301-1218 of SEQ ID NO: 13, or with a probe which can be prepared from the same nucleotide sequence, said DNA encoding a protein having DNA binding activity. 
 
     
     
       5. The bacterium according to  claim 1 , wherein said bacterium belongs to the genus  Escherichia, Enterobacter  or  Pantoea.    
     
     
       6. A method of producing an L-amino acid selected from the group consisting of L-glutamic acid, L-arginine, and L-threonine, comprising:
 A) culturing the bacterium according to  claim 1  in a medium to allow the L-amino acid to be produced and accumulated in the medium or bacterium; and 
 B) collecting the L-amino acid from the medium or bacterium.